Optical system for the inspection of curved profiles



Aug. 19, 1952 2,607,267

OPTICAL SYSTEM FOR THE INSPECTION OF CURVED PROFILES A. R. FULTZ ET AL 8 Sheets-Sheet 1 Filed March 29, 1950 FIG. 2.

L4 2 1 p 1 N l/WKJ W 6%? I Q J J T \%fl ,M N A w R w \W/ m 7 Z a z z H H i Aug. 19, 1952 A. R. =FULTZ ETAL 2,607,267.

OPTICAL. SYSTEM FOR THE INSPECTION OF CURVED PROFILES Filed March 29, 1950 8 Sheets-Sheet 2 FIG. 4.-

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"WIIIIIW- ALLEN R.FULTZ ROBERT J. HUDAK INVENTORS i m BY W I ATTORNEYS 1952- A. R. FULTZ ETAL 2,607,267

OPTICAL SYSTEM FOR THE INSPECTION OF CURVED PROFILES Filed March 29, 1950 8 Sheets- Sheet 3 FIG.6.

ALLEN R. FULTZ ROBERT J. HUDAK INVENTC R5 ATTORNEY Aug. 19, 1952 A. R. FULTZ ET AL OPTICAL SYSTEM FOR THE INSPECTION OF CURVED PROFILES Filed March 29, 1950 8 Sheets-Sheet 4 ALLEN R. FULTZ ROBERT J. HUDAK INVENTORS W 9. BY WM.

A T TORN E YS Aug. 19, 1952 A. R. FULTZ ET AL OPTICAL- SYSTEM FOR THE INSPECTION OF CURVED PROFILES- 8 Sheets-Sheet 5 Filed March 29, 1950 m U E R wmim f WA N T W m H Aug. 19, 1952 A.-R. FULTZ ETAL 2,607,267

. OPTICAL SYSTEM FOR THE INSPECTION OF CURVED PROFILES Filed March 29, 1950 8 Sheets-Sheet 7 ALLEN R. F ULTZ ROBERT J. HUDAK INVENTORS.

ATTORNEYS Aug. 19, 1952 A. R. FULTZ ETAL 2,507,267

OPTICAL SYSTEM FOR THE INSPECTION OF CURVED PROFILES Filed March 29, 1950 8-Sheets-Sheet 8 FIG. 13.

ALLEN R.FULTZ ROBERT J. HUDAK INVIENTORS BYWIM 2M...

ATTORNEYS Patented Aug. 19, 1952 OPTICAL SYSTEM FOR THE INSRECTION OF CURVED PROFILES Allen R. Fultz and Robert J. 'Huda'k, Rochester, N. Y., assignors-to'Eastman Kodak'fiompany, Rochester, 'N.'Y., a corporatiorrof -New Jersey 7 Application March 29, lesaser mo. 152,546

.Thisinvention relates to contour projectors suchas used in machine shops for the inspection of machine parts.

It is the object of the present invention to provide an optical system for the examination of the complete profile of a cross section of a test object. It is also. a primary object to permit such inspection of profiles which cannot be viewed orthogonally. Most profiles must be viewed obliquely if the object itself is to remain in one piece.

It is an objector certain embodiments of the invention to examine the complete profiles of two cross sections of asingle object and to compare them one with the other. In this connection, it is the object of the invention to project images of two complete profiles superimposed on a viewing screen.

It is an object of a preferred embodiment of the invention to illuminate the complete profile which is to be inspected by means of two illuminating systems only. Complete illumination from all sides, 1. e. covering 360 can, in most cases, easily be obtained with illumination from three or more directions, but according to this preferred embodiment of the invention, only two illuminating systems are used, and these are located on opposite sides of the object.

It is a further object of the invention to project the images from the cross sectionunder test in such a manner that the main'advantages of ':the Turner and Kingslake projection system described in copending application Serial Number 64,404 filed December 9, 1948, now Patent No. 2,552,238 of May 8, 1951, are obtained in the present instrument. These advantages include a large working space to accommodate various objects under test and a choice of magnifications for viewing of the image without afiecting' the working space. In this-connection it is a special object of one embodiment of the present invention to arrange the projection lenses of theoptical system, as required for the advantages just mentioned, in a convenient combination withthe reflectors which are essential to the present invention for obtaining the complete profile in ;a single image. Incidentally the present invention is the first application of the Turner and Kingslake system to oblique inspection.

In connection with the embodiment of the inventionv which permits the simultaneous, or rapidly successive, inspection of .two different sections,.-one preferred feature or group of features permits these sections to be either very far apart or very close together. The illumination '18 Claims. (01. 88 24) P p of two sections close together by separate optical systems would' normally involve mechanical int'erference of the illuminating systems, but. the preferred feature here referred to eliminates this interference without spoiling the effective-' ness of the illuminating systems. l J

According to the invention the above objects, are lobtainedby an optical :system which includes; a plurality of illuminat'ors'ifor illuminating ,a line around the object under test. That is the profile of the section is illuminatedby aline-o'f light; This may be .done by merelyshining light through a slit so that the shadowof the mask .in which the slitis formed defines the line of light,"jbut preferably images of illuminated slits are formed on the-object. A pluralityof objectives are also uniformly s'paced around the object to receive the light obliquely reflected from the line of illumination. The objectives are all substantially at the same obliquity and form images of the parts of the line seen by the objectives. According'to the invention a pair of mirrors is op-j tically aligned with each of the, objectives .for reflecting the images into register andfor mak ing these aerial images parallel to the original I section oi the object which is illuminated. Furthermore, the images of thisprofile are perpen dicularly spaced ,from the section whichpthey rep-' resent. i I g If the object under test is considered tofhavean axis perpendicular 'to the, section being examined, the images .are in register on this axis or around the axis and .are also'in a 'planeperpen diculartothis axis." I

Preferably the aerial images thus'registere'diare relayed by a projection lens whichreceives light from the images and forms a magnified image thereof on a screen for convenient viewing. ,Pref-;

erably th objectives whichreceivelight from the profile'under test and form the first aerial image are 'afocal objectives consisting of twovpositive lenses (usually but-not necessarily of equal power) separated by the, sum of their focal lengths. For the sake of compactness, at least one ofthe mirrors associated with, each objective is optically between the two positive lenses which make up the objec tive in this aiocal case.

Preferably there are only two illuminatingsys tems'for each section and they are located on opposite sides .of the-object. The obliqueiproe jection systems include twov objectives on the same .opposite sides .of the object as the illumi-. nating systems, for receiving the obliquely ,reflected'light. ,If the illuminating systems form a beam of light diverging towardthe object; th

edges will not be illuminated, but when each of the illuminating systems includes positive lenses,

wider than the object and arranged to form converging beams of light on the opposite sides of the object, these beams overlap each other around the edges of the object so that a complete profile is illuminated. The last lens of the illuminating system is said to see over-the-hill with respect to the object in this case; the lens sees around both sides of the object. To insure a definite line of light accurately defining the (profile in question, the preferred embodiment of the invention employs illuminating systems including an illuminated slit in each case and an objective for forming an image of the slit on the object. To provide sharp edges to the lineof light on the profile, the illuminated slit is approximately, and preferably precisely, conjugate to the part of the object which is illuminated thereby. H

f Preferably,the illuminating system, as well as theobjective system includes an aiocal objective consisting of two positive lenses separated by the sum. of their focal lengths. In this case, the

object ,is obtained by using a slit which is approximately, preferably. exactly, the same shape asthe side .of the object which it is illuminating. Various methods of forming such slits maybe used Extremely precise work for example, employsa sheet of glass molded on the object itself and then provided with a black coating in which ajslit is engraved or etched.

. Iniorderto permitthesimultaneous viewing of the images of the profiles of two different sections of the object, specifically two parallel sectionsof the obj ect, the present invention provides a duplicatefset ofilluminating systems. The image of the firstlprofile is projected as described above, but a plane reflector is located in the beam parallel to the'section so that the light from the second illuminated profile, reflected obliquely by the sec- Qndsection, is reflected by the mirror into alignment with the direction of the beam of light from the first section. To obtainthis efiect, the mirror is parallel tolboth sections or profiles and is located' half-way between them. In one embodiment, this mirror is semi-transparent so that images ofboth sections are formed simultaneously. In another embodiment, the mirror is fully reflecting and is mounted to be quickly movedin and out of place for viewing the images of the two sections in rapid succession. Images of the two profiles are thus superimposed or eifectively superimposed and the axis of the object as discussed above in connection with this optical systemis, by the nature of the optical system,

superimposed for the two images. Manipulation of the object itself will move one of the images relative to the other until this axis corresponds to-some'desired axis in the object.

For example,- in the construction of turbine blades it'is desirable to know the exact location of the axis thereof defined by the line which passes through the center of gravity of the blade sections. This line may-or may not be straight, dependingon the shape of, the blade, but for the purposes of the present example, it is assumed thatthe operator is interested in the location of the axis is a turbine blade which has such an axis straight. The operator places the turbine blade in the present instrument and then recognizing the center of gravity of the cross sections, or more exactly of the images thereof, he manipulates the turbine blade until these two ing details of the image forming sections are registered in the images. He then knows that the axis of the object which he is seeking is on the axis of symmetry of the instrument.

In testing certain objects, it is desirable to compare profiles of sections which are quite close together. The distance between the sections under examination may be varied merely by moving the illuminating systems toward or away from each other while maintaining the semitransparent mirror half-way between the planes defined by the illuminating systems. However, when the sections are very close together, there is mechanical interference between the optical systems which constitute the illuminating means. To overcome this, a preferred embodiment of the invention employs four illuminating systems including lenses of semi-circular profile with the fiat side of the lenses inthe systems on each side of the object facing toward each other. When such illuminating systems are moved toward each other, there is a minimum of mechanical interference. At the same time the effective diameter of the last lens of each illuminating system is not reduced as far as the ability of this lens to see over the hill, 1. e. around the edges of the object, all as discussed above. When each of the illuminating systems consistsof an afocal lens, only the second positive lens in each case has to have this semicircular profile. A mirror may be included between the second and the first lenses of the afocal system so that'the first lens may be to one side for one of the profiles and to the other side or, even to the same side but longitudinally displaced, with respect to the other profile so that there is no interference of these first lenses when the illuminating systems are moved toward each other.

The operation of the invention and other objects and advantages thereof will be fully understood from the following description when read in connection with the accompanying drawings in which:

Fig. 1 is a perspective schematic view of one embodiment of the invention.

Fig. 2 is a vertical section shown in Fig. l.

Figs. 3 and 4 are schematic showings of optical systems to illustrate the principle of over the hill illumination.

Fig. 5 is a schematic perspective View of one part of the optical system of a preferred embodiment of the invention.

Fig, 6 is a similar view illustrating the addition of the two-section feature.

Fig. '7 is a similar view illustrating the addition of the semi-circular lens feature.

Fig. 81$ a perspective view of part of the illuminating system and its mount in the preferred embodiment of the invention.

Fig. 9 is a similar view of the objective system employed in the invention.

Fig. 10 is a vertical section through the optic axis of this preferred embodiment with certain of the mounting features shown but in minimum detailto avoid confusion.

Fig. 11 is aplan view of this embodiment showof the embodiment of the illuminating system. Fig. 12 is an end view showingpart of the illuminating system.

Fig. 13 is a perspective view of the whole optical system with certain details cut away or show merely in outline to avoid confusion.

system but not :Fig; Iiisi au'rear view of T5118 :detaih (the? mirror mount) of theinstrument."

:Fig. is a .perspectiveview of 2the" o'uts'ide of the-instrument.

'In Figs. -1 and 2 the objectto be examinedis shown asaa cylinder Ill. -A.line of light H around this object it at'aone :planesefition thereof and. constituting the profile :at this :section, iscproduced: by slits .L2, z'illuminatediby'lamps l;3;:so that' images of these :slits focused :by :objectives d4. onto'ithe' object form thezre'quired line -oilightzbl. For thesake of generality the optic axes of the lenses M impinge on the object lOJat points '15 and .16 which are different Tfrom the axesof the objectives which are'to form'images of the fprofile in question. Preferably the slits P2 are curved, as shown, conjugate-to :the part of the ;object t0 whichthey areto illuminate.

"Three beams of light "represented byrays 20, obliquely reflected from the object, i'arefo'cused respectively by three lenses 2| and'a'pair ofrmirrors 2-2 and-23 associated :with each lens, toform images .24 in register in a plane parallel to the section .l-"l :andrperpen'dicularly spaced therefrom. The object It! is normally a diffuse object sothat light from the line H goes out in all directions. Since'most objects havesomespecular reflection in addition to their diffuse reflection, a maximum brightness is obtained by insuring that a maximum amount of light from the lenses strikes the line H obliquely from the side opposite to that in which the rays leave the line I I. This is 'importantlater in connection with the embodiment of the invention'whioh uses half lenses or lenses of semi-circular profile. If the lenses M are cut down the middle'and only one half thereof is used, it is better to have it on the far side of the line i I so that a maximum amount of light is traveling in the direction of the rays 20. This is exactly what happens in the semi-circular lens case discussed below, which is fortunate.

It will be noted that the image 24 is in a plane orthogonal to the axis 25 of the object ll). of course, the object [0 may not be a symmetrical one, or may not be oriented orthogonal to the section H, but the axis 25 in question is one perpendicular to the section H and in every case, the image 24 is in a plane parallel to the section H.

The use of three illuminating systems and three objective systems insures that the whole profile is examined, except possibly for some very unusual object, but the tripling of the number-of optical systems is quite expensive and the mounting' thereof spaced at 120 is not too convenient and therefore it would be preferable to use only two illuminating systems and two objectives. Such an arrangement requires a special form of illuminating system if the profile image is to'be uniformly bright. The reason for this is "illustrated in Figs. 3 and 4.

In Fig. 3 the object is illuminated by elongated light sources or slits 32 focused by lenses 3-! whose aperture or diameteris not-appreciably greater than that of the object 38. It does not matter how long the light source or secondary light source 32 is. The only light which strikes the object 30 is that-from between the two points 33 for example. Light from the point 33 reaches the point 35 on the object '30 through-one-side of the lens but does not reach even this point via the other side of the lens. All of the points of the object .30 between the point 36 and the point-38 are :fully illuminated but the intensity of illumination falls :off between the points and 34 and 6 there :is-no illumination beyondthapoint '34 hom the :upper illuminating- -system. Similarly there is .no illumination beyond the point 39 from the lowerliluminating system, and-thus all;p,oint between -.:34 and 39, such as the point -35,- are not illuminated atall. The point 31 could-illuminate beyond the point 34 if it were not for the shadow of athle object 30 itself.- In Fig. ithe only differonce is the substitution of -lenses 43 whichhave a :larger aperture. The fact that thediameter of the. lenses 43 is greater thanthat of the object 30 allows the lenses to see over the hill. Light from therpoi-nt'iil inthis case actually reachesthe point -41 and similarly-light from the lower slit 32 can :reach the :point 42. The point 3,5,o the 01118613230 is illuminated by both illuminating .systems. Thus "by :the simple expedient ':of using large aperture lenses, complete :-illumination of the profile is I obtained with onlytwo illuminating systems. It should *be :noted that the diameter of the lenses 4% i -the direction parallelto the profile ,under question is the effective diameter. The lenses 43 may be cut in half the other way orthe other diameter thereof may be reduced-in any desired tmanner without affecting the ability of the lenses to see over the hill for theabove dlSCUSSGdrPHIYPOSG.

The preferred-embodiment of the invention will now :bedescribed in detail, Theinvention refers onlyto the'optical system. The mechanical'means for holding the object :under 'testand for manipulating it are shown only schematically since they :are not an essential part of thetpresent invention. Further to simplify the explanationof the optical system, schematic Figures 5.6 and 7 are included, in which the component parts of each .lens and the :mount for each lens "is omitted. Furthermore, the discussion is confined t0 the 'system on -one"side of the object, it being understood that there is an identical optical system onthe opposite side ofthe object 'ineach case. 'Theentire profile of a section is projected by matching the half profiles seen in the Figs. 5, 6'and '7.

- In Fig; 5a turbine blade 50 is positioned and held so that a section 51 is illuminated and examined by the instrument. Light from a lamp 52 through acondenser '53 uniformly illuminates aslit54 which is'curved Ito matchapproximately the section "51.; An image of this 'S1itT5'4 is proj-ec'ted by an afocallens :55 onto the section -5l and'fits closely to this section. Light from the section 51 is projected obliquely by an afocallens made up of positive lenses 6E! and BI separated optically "by thesum of their focallengths. Miritito a screen 61 forming a greatly enlarge'dsimage 68 thereon.

The following discussion will begin with th light source and explain the function of each element of thesystem.

Ltglht eource.-The most desirable and optically e'fiicient light source is a single lon source of small cross-section. The capillary o'f the-mercury lam-p is of small cross-section and can'bevobtained in sufiicient length for this application. Furthermore, there is no-saggingior other displacement of the luminous mercury column with reference to the optical system as would be encountered in using a tungsten filament, The form of the light source is not a critical part of the present invention.

Condensing Zena-A condensing lens of large diameter or aperture collects as much of the total light emitted by the source as practical and concentrates it through a narrow slit cut in a metal ribbon or scribed in an aluminized glass plate, so as to fill the afocal lens 55. A second function of the condensing lens is to concentrate all of the light source on the slit. The illuminated mercury column is of a fixed length; in one type of lamp commercially available it is three inches long. On the other hand, the slit is preferably as long as the chord of the section being projected when conjugate thereto with respect to a lens 55 working at unit magnification. A turret of condenser lenses may be used for special purposes, but this is not usually necessary.

SZzt.The slit serves the purpose of baffling all of the light coming from the source through the condensing lens except a narrow band which is projected to the blade by the primary relay lens system. The slit performs two functions. First, the'edges of the slit sharply define the boundaries of the band of light falling on the blade. One of these boundaries in turn defines the profile of the blade on the screen, as will become more apparent later; Second, by curving the slit to the approximate profile of the blade section, the light from it can be projected to the blade without encountering depth of focus difficulties in the primary relay lens. If a straight slit were used at all times, then the primary relay lens which projects it would have to be stopped down or, in other words, its aperture reduced, until the lens had sufiioient depth of focus to project the straight slit on a curved blade and still maintain the proper focus at the blade. However, reducing the aperture of the lens reduces the light that can pass through it as the square of its diameter, so that such an arrangement is totally unsatisfactory if the blade has any appreciable curvature. An example will make this point more apparent. The primary relay lenses as designed for this machine have an aperture of F/2.1. At this aperture they will tolerate a depth of focus variation between the object and the image of only about .040 inch. If a variation between the shapes of the slit and the blade of /2 inch were desired, the lens would have to be stopped down to an aperture of F/22, and at this reduced aperture the light passing through the lens would be decreased to .009 of its former value.

Primary relay Zens 55.As mentioned above, the relay lens 55 projects the band of light coming from the slit to the corresponding section of the blade. The primary relay lens is actually two independent lenses of equal power separated by twice the focal length of either. This system has the advantage over a single lens of working at a much higher aperture and has no distortion. The

a system has sufiicient back focus so that interference of the lens mounts with other optical beams axis 65 at any desired magnification (1:1 in the example shown). This transfer is accomplished 8. by the lens elements themselves, while the orientation on the axis 65 is done by two mirrors 62, 63 built into the relay system. The reason for using a secondary relay lens is first, that it is not practical to design a. 10 or 20 power projection lens having sufficient back focus to view section A and still clear the end of a 9 inch long blade for example, unless a great deal of variation could be tolerated in the position of the screen for various magnifications; second, this necessary clearance would require a 10X lens of almost prohibitively large diameter. Consequently, the relay lens places the image of the section in a position which is unobstructed by the blade itself, so that this image can be viewed by a projection lens of any power. In fact, in setting up the machine this first image 64 is critically examined using a microscope in order to check the alignment of the various mirrors. The relaying of this image by lens 65 to screen 5'! is not an essential feature of the invention but merely provides convenient viewing of the images.

The secondary relay lens and .6!) views the light band at section 51 at an angle of 25 degrees with the axis 55. This angle has been arbitrarily chosen.

Projection Zens.'As the name indicates, the projection lens 66 views the first image and projectsit at a specified magnification on a screen which in this embodiment is translucent but of course could reflecting. Since there are no restrictions on the back focus of the projection lens, one can be designed for any magnification as long as the practical limitations imposedby the screen size and the amount of light available are met. Magnification changes are easily made by mounting various projection lenses in a turret and indexing to whatever magnification is desired.

Screen.-Either an opaque or a translucent screen 6? could be used, but the opaque screen has the disadvantage of forcing the observer to assume a position which interferes with the light striking the screen, so that a translucent screen is more practical. Ordinary ground glass is a satisfactory screen material.

Fig. 5 is similar to Fig. 5 in all respects except forthe addition of a mirror '55 and a second illuminating system for illuminating another section II of the turbine blade 50. As in Fig. 5, only the upper half of the system is shown and considered here. A duplicate system illuminates the lower side of the section 7!. Elements l2, 13, i4 and l5'correspond exactly to elements 52 to 55. Light from the profile H is received by a semi-transparent mirror 16 which reflects this light into alignment with the beam from the section 5|, which in this case is transmitted by the mirror 16. Thus a second image ll is superimposed on the image 64 and both of these images are projected by the lens 66 to the screen 61. The images 68 and 13 thus formed are superimposed and a certain point in each profile falls on the center of the screen corresponding to the axis 65. In Fig. 6, dotted lines have been provided to show the complete images 68 and 73. The lower half ofeach image, i. e. the part shown by broken lines, is produced by the corresponding optical systems (not shown) below the axis 65. By manipulating the blade 50, the images 68 and 18 may be moved on the screen until the center of gravityof both sections are superimposed on. the center point which corresponds to the axis 65.

It is noted that the lens '69 can see through the half-silvered mirror 16 to receive light from section H to the mirror are equal. Thus both.

sections H and 51 are brought into. proper focus and projected, simultaneously. Toeliminate any.

error due to. the thickness. of glass. carrying the half-silvered mirror, which wouldintroduce a slight. difference. in the optical path length, the mirror is kept. as thin. as possible. .P-elliclesare usually used for this purpose. A, full silvened mirror at 16 reflects the. section H and-forms images I! and 18 only. In this. case, the mirror is mounted to be moved out of the Way. for eX-r.

amination of .images 64. and 6812f. section 51. While this alternative embodiment means thatvv the. images are not projected simultaneously, nevertheless rapid movement of the mirror Iii back and forth in and out of the position shown is .in practicequite satisfactory and there is little objection to the fact that one sees only oneimage The use of a full silvered .mirror.

at a time. doubles, in fact more than doubles, the brightness of theimages as compared to a semi-transparent, semi-reflecting mirror. Thus both arrangements have advantages- In Fig. 6 the section II maybegatany distance,

from the section i provided the mirroror semitransparent mirror 16 is half-way between the sections and secondly provided that the lenses 5 5 and 15. do not interfere with each other me chanically. The, purpose of the arrangement shown in Fig. '7 is, to overcome this second limita-. tion and to permit the sections 5-1 and 'H :to be selected very close together.

In Fig. '7 the section 51 is illuminated :by light from a lamp 89 through a condenser BI and a curved slit 83 matching the section 5|. As difierent sections of the blade are selected,. difierent slit curvatures are required for absolutely precise illumination. Therefore a turret 82 of slits provided and different slits are moved into the light beam as difierentsections of the blade are.

to form the line image 5!. .Thelens .84 may he a full lens or only half of .a lens without the section which :is blacked out in the drawing.

However, according to the special feature of this embodiment of the invention the lens 8.6 is only a half lens, 1. e. one with semi-circular profile with the hat side facing toward the other ii'lluminating system. A mirror 185 reflects the light from lens to the lens 86. j

The section M is simi-larly illuminated by a lamp 90, .a condenser .lens 9i, a :slit '92 and an afocal lens made. up of positive .lenses 9?; and 95 with :a mirror #95 between'zthem. In this afocal projection lens made up of. lenses 69 and.

case the lens 94 maybe, and the. lens 9imust be, a half lens of semicircularprofile. The light beamv for this second. systempassesaboye the beam. for the first. system before reflection by the mirror. 95. The mirrors v and 95 may be oriented in. various. directionsand may even be oriented inthe same direction providing one is in a higher plane than the other. It will be seen that as. the illuminating. systems are moved to ward each. other, mechanical interference. is reduced to a minimum and the sections 5]. and H may be selected .quite .close together.-

Figs. 8. to 14 illustrate a preferredembodimcnt of the. invention incorporating all of the features discussed above. The mirror 16 is shown as a semi-transparent pellicle rather than a full silveredmirror mounted on a turret to. be moved in and .out of place, but both arrangements are useful, as has been mentioned. Since the present invention relates to the optical system, these drawings illustratethe details of the optical s-ys-s tem and the mounts therefor butdonot. bother to go into great detail with respect to the mechanical system for manipulating the workpiece under examination; As far. as the presentinvention is concerned, any. mechanical system isv satisfactory for this purpose.

In all of these figures, the reference numerals arethe same as those used in Fig. '7 where .corre-. sponding parts are shown.and.the..duplicate.sys-. tem which illuminates and projects. the image of the lower side of each sectionusesthe correspending numeral added to... 19.9.. For example, the light source corresponds to the lower light. source 1.90 and the .slit .92 corresponds to the lower slit I92. I

Fig. 8 shows the. upper and lower optical syse,

tems for illuminatingkthe section "H on they turbine blade 50. The. last lenses B16. and 1.8.6.

of the system which illuminates section 51 are also shown in Fig. 8 but the rest of these systems are omitted from this particular figure. It will be noted that thewhole optical system is. longitudinally movable on tracks to permit the selec tionof different sections 'Tll ofthe blade .50. Either mechanical or electrical .driving mechanisms can.

be used for this purpose. This isnot an essential feature of the invention and in .the arrange: ments shown, simple .turn= wheels engaging pinions riding in racks provide. the necessary motion.

Fig. 9 illustrates the preferred mount for :the

Si and mirrors 162 and 63, and their .correspond-.

ing counter parts I60 to lfiitbeglowcthe ,axisziifw It'will be noted that the lens s ffifl andfiil and the mirrors '62 and 63 aremountedrotatableandthey are adjusted to insure that the image .94 is not. only on the axis Giilbut is in a planeorthogonal to the axis 155. The projection lens .66, including a field. lens. near the ima ev 1614., is als shown in thisF-ig. 9. 1

A1 of t e e p rts a so-appear i he, vertic l section which constitutes Fig, 1-9. semitransparent mirrorl 16, is shown in this fig ure. It will .be noted-that the blade ,Enis men 1;.-

edin a chuck-or clamp which can be m (d longitudinallyof the axis 5.5., secondly which be rotated about his a is and thirdl can be rotated about axes atrigh angles itofthe axis. 65 at-the center of curvature of a spherical bearing 209 which constitutes ;part of the-clamping mechanism. 'This center of curvature is in the plane or section 5!; thus rotation-of a'test blade 50 to :adjust the section :H does not aifectbthe Th inne adjustment of .the first section I. The clamping and manipulating mechanism is not an essential part of the optical system and therefore is not described in detail. In a simple embodiment of the invention the device is held in the mount shown merely by friction and is moved by hand. In more elaborate embodiments, electrical drives are provided and servo mechanisms are coupled to indicators or subsequent stages in which the blade is to be mounted for further manufacturing operations.

Also Fig. shows for the first time the fact that the objective 56 is mounted on a turret so that different magnifications can be selected at will. A mirror I0! receives th light from the objective 66 and reflects it to a screen adjacent to the operator. As shown in Fig. 11 this screen I02 which is the equivalent of the screen 6'! of Fig. 7 is mounted at an angle for ease of viewing.

' Fig. 11 is a top view showing the relationship between the lens and mirror system 68 to 63 and the mirror WI and screen I02. To permit aquick check on the orientation of mirrors and I16, which must be held within close toler ances, collimators 2 of the gauss eyepiece type are included, each with a lamp 2I3, a reticle 252, a semitransparent mirror '2I5 and a lens 2M to send collimated light to the mirror 16 or H6 and to refocus it after reflection on a second reticle 2I6, which can conveniently be examined through a telescope 2I1.

Fig. 12 is an end view mainly showing the illuminating system made up of elements '89 to 86 and the corresponding lower system made up of'elements I80 to I86 respectively. Lenses 94 and I94 of the other illuminating systems are shown. As shown in this figure the mirrors 16 and I16 are mounted rotatable about pivot 19 I and I19 which are ofi set slightly so that the rotating parts do not interfere'with each other. This permits the mirrors 16 and I16 to be full silvered mirrors rather than semitransparent ones. As pointed out above either embodiment has advantages.

Fig. 13 is a perspective view (partly broken away) of all of the component parts of the optical system. No additional features are added in this figure. The coupling between the two illuminating systems so that the mirrors 13 and I16 are maintained half-way between the two sections being illuminated and examined, consists of simple levers which do not appear in this- Fig. 13 since they would confuse the drawing. Therefore they are shown in Fig. 14'. (On the same sheet as Fig. 8.)

In Fig. 14 the only parts ofthe optical system shown are the lenses 86, I86, 96 and I96 and the.

mirrors 16 and I16. The view is from the'opposite side to that shown in Fig. 10. The mirrors 16 and [16 are carried by a mount comprising a vertical portion 2IlI and a horizontal portion 202 which slides between horizontal tracks 2M.

' A gudgeon 203.extendingfrom the side of the mount 202 acts as a pivot for two lever arms 205, the four ends of which contain slots 2% which engage pins 201 on the sides of the condenser lenses. Movement of either of the illuminating systems toward or away from the other system provides a corresponding motion of the point 203 but with only half the extent of movement. Thus th mirrors I6 and I16 are maintained exactly half-way between the illuminating systems.

Fig. 15 is merely a perspective view of the out- 12 side of the instrument to indicate the overall dimensions thereof.

Our invention is not limited to the specific arrangements shown but is of the scope of the appended claims.

We claim:

1. An optical system for the inspection of the complete profile of a cross section of an object, comprising .a plurality of illuminators for illumi nating a line around the object at said section from a plurality of directions covering 360, a plurality of objectives uniformly spaced around the object for receiving light reflected obliquely from said line, with substantially the same obliquity for all of the objectives, and for forming images of parts of said line, and a pair of plane mirrors optically aligned with each of said objectives for reflecting said images into register parallel to, and spaced directly perpendicularly from, said section.

2. An optical system according to claim 1, including a screen and a projection lens for receiving light from the registered images and for relaying them, with magnification, onto said screen. 7

3. An optical system according to claim 1, in which each of said objectives is afocal consisting of two positive lenses optically separated by the sum of their focal lengths.

4. An optical system according to claim 3, in which at least one of the two mirrors aligned with each objective is optically between the two lenses of the objective. v

5. An optical system for the inspection of the complete profile of a cross section of an object, comprising two illuminating systems on opposite sides of the object for illuminating a line around the object at said section, two objectives on the same opposite sides of the object for receiving light reflected obliquely from said line, with the same obliquity for both objectives and for forming images of the corresponding opposite parts of said line and a pair of plane mirrors, optically aligned with each of said objectives, for reflecting said images into register parallel to, and spaced directly perpendicularly from, said section.

6. An optical system according to claim 5 in which the illuminating systems include positive lenses wider than said section of the object forming converging beams of light on said opposite sides of the object with the two beams thus formed overlapping each other around the object.- a

'7. An optical system according to claim 5 in which each of the illuminating systems includes an illuminated slit and an objective for receiving light from the slit and focusing an image thereof on the object.

v.8. An optical system according to claim 7 in which said illuminated slit is curved to be conjugate to the side of the object illuminated by the image of said slit.

9. An optical system according to claim 5 in which each: illuminating system includes an illuminated slit and an afocal objective consisting of two positive lenses separated by the sum of their focal lengths for receiving light from the illuminated 'slit and forming an image thereof on the side of the object. a

10. An optical system according to claim 9 in which the slit is the same shape as the side of-the object and is precisely conjugate thereto.

11. An optical system according to claim 5, including a screen and a projection lens for rel3 ceiving light from the registered images and for relaying them, with magnification, onto said screen.

12. An optical system according to claim 5, in which each of said objectives is afocal consisting of two positive lenses optically separated by the sum of their focal lengths.

13. An optical system according toclaim'lZ, in which at least one of the two mirrors aligned with each objective is optically between the two lenses of the objective.

14. An optical system for the simultaneous inspection of the complete profiles of two parallel cross section of an object, comprising four illuminating systems, two on opposite sides of the object for illuminating a line around the object at one of said sections and the other two on the same opposite sides of the object for illuminating a line around the object at the other of said sections, two objectives also on the same opposite sides of the object for receiving light reflected obliquely from one of saidlines past the other of said lines, with the same obliquity for both objectives and for forming images of the corresponding opposite parts of said line, a semitransparent reflecting surface parallel to said sections and half-way between them for reflecting light from said other of said lines into alignment with the direction the light goes to each of the objectives for forming images of oppositeparts of the second of said lines superimposed on the plane of the first mentioned images, and a pair of plane mirrors, optically aligned with each of said objectives, for reflecting each pair of superimposed images into register with the other pair, parallel go, and spaced perpendicularly from, said secions.

15. An optical system according to claim 14 inv which the distance between the two sections is adjustable, th illuminating systems are adjustable accordingly, and which includes means for adjusting said systems and semitransparent refleeting means in each object beam parallel to itself to maintain the reflecting means half-way in which at least one of the two mirrors aligned with each objective is optically between the two lenses of the objective.

- ALLEN R. FULTZ.

ROBERT J. HUDAK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,066,996 Morioka Jan. 5, 1937 2,163,124 Jeffreys' June 20, 1939 2,256,102 Reason Sept. 16, 1941 2,302,572 Reason Nov. 17, 1942 2,349,989 Reason May 30, 1944 W011i Mar. 7, 1950 

